In today's business world, there are a variety of printers in widespread usage. These commercially available printers are generally used as output devices for digital processors such as, for example, word processors. A substantial number of these printers are impact printers which, as defined herein, is a printer having a molded character which impacts a ribbon which makes contact with the paper. As is well known in the art, the print quality is optimized when the paper is secured against a firm surface. Accordingly, most of the printers utilize conventional typewriter paper path parts comprising a platen roller, guide plate, feed rollers and paper bail roller assembly. Generally, a movable carriage assembly is used so that the platen is stationary. Many of the carriage assemblies have a daisy print wheel whereby the molded characters are at the ends of spokes which fan out from a hub. Also, many printers use bi-directional printing which means they print when the carriage assembly is moving in both directions.
Because speed and operator convenience are important operational parameters for printers, many automatic paper feed mechanisms have been introduced to the marketplace. One of these commercially available paper feeders will be described, but it is understood that the description or a slight deviation from it will be applicable to many other automatic paper feeders. The paper feeder mounts on the top of the printer and a mechanical arm from the feeder is connected to the paper bail roller assembly. When a sheet of paper is to be fed into the printer, the paper feeder feeds a sheet of paper into the paper path of the printer until it reaches the position where the platen roller contacts the first row of feed rollers. Simultaneous to or immediately after this action, the paper feeder opens the paper bail assembly by activating a solenoid which controls the mechanical arm. Then, the paper feeder provides a series of line feeds to the printer, which sequence advances the paper through the paper path to a typing position which is approximately one inch below the top of the paper. Next, the solenoid is deactivated and a spring in the paper feeder causes the mechanical arm to retract so as to close the paper bail assembly on the paper. After completion of printing on that sheet of paper, the paper feeder controls the ejection of the paper and the automatic insertion of a new sheet of paper as previously described. In a typical office scenario for a word processor application, the operator types a page of text into the word processor and depresses the PRINT key to initiate the printing process. Frequently, the printer and paper feeder are enclosed in a sound shield to reduce the noise in the environment. When the printing on a sheet of paper is completed, the sheet of paper is automatically ejected and a new sheet of paper is fed into position with the paper bail assembly being opened and closed at appropriate times. Without opening the sound shield, the operator may then continue to type the next page of text and at some later time repeat the printing process.
It was found that there are circumstances where it is desirable to have the first line of text at the top of the paper instead of down approximately one inch. To provide this feature, the paper feeder was modified so that a fewer number of line feeds were transferred to the printer for advancing the paper through the paper path during automatic feed; this advanced the paper only to a position where the first line of text was at the top of the paper. However, it was determined that if the paper bail assembly was closed with the paper at this position, the paper would jam when it fed up to the paper bail assembly position during printing. Furthermore, because it may be an extended period of time before the next PRINT function is executed as described above in a typical operational scenario, it was undesirable to electronically delay the closing of the paper bail assembly until several lines of text had been printed. To delay deactivation of the solenoid, the power supply for the unit would have to be larger to maintain activation of the solenoid simultaneous to other functions. Also, a large amount of power would be consumed by the power supply. Further, the deactivation of the solenoid during the printing cycle could cause power spikes and interference which would adversely affect the printing.